Diagnostics

NPCT

New Parametric Current Transformer

DC non-destructive beam current measurement

Bandwidth

DC to 10 kHz

Resolution

< 0.5 µArms√Hz

Principle

The NPCT works on the principle of the zero-flux DC current transformer (DCCT). The DC component of the current flowing through the toroid sensor is detected by a magnetic modulator also called fluxgate or second harmonic detector. The AC component is detected by a AC Hereward transformer. The two circuits are cascaded in a common feedback loop to generate a magnetic flux which always cancel the primary current flux. The NPCT output is the voltage developed by the feedback current passing through a precision resistor.

Application

Parametric Current Transformers are used on most particles accelerators in the world to measure the average beam current. They are essential instrument for machine tuning, commissioning, operation and machine/personnel safety.

The large dynamic range, the wide bandwidth and high resolution make it the ideal instrument to measure beam lifetime in storage rings.

It is often the only truly calibrated beam instrument in an accelerator and serves as a reference to calibrate other beam diagnostics.

2 packaging types for the NPCT sensor

In-air NPCT installation, over the vacuum chamber. Requires installation of a “gap” to prevent the wall current from flowing through the NPCT aperture. The gap can be a brazed ceramic ring or an organic material O-ring depending on the vacuum requirements. Typical installations include bellows, a wall current bypass and an electromagnetic shield enclosing the NPCT completely.

In-flange NPCT is mounted in the beam line.

Short axial length, includes a ceramic gap vacuum-brazed to kovar.

Does not require bellows nor wall current bypass

Available from CF2“1/8 to CF8“

UHV compatible

In-air NPCT installation, over the vacuum chamber. Requires installation of a “gap” to prevent the wall current from flowing through the NPCT aperture.

The gap can be a brazed ceramic ring or an organic material O-ring depending on the vacuum requirements.

Typical installations include bellows, a wall current bypass and an electromagnetic shield enclosing the NPCT completely.